Retinal Transduction Lec11 Flashcards Preview

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Flashcards in Retinal Transduction Lec11 Deck (99):
1

what is the fovea? the small depression at center of macula with the ___

 highest spatial acuity

2

what enters and leaves the optic disk?

blood vessels enter and retinal axons leave the eye

3

: ant. ciliary and long post. ciliary arteries  supply blood to the

iris and ciliary body

4

Uveal tract consists of three structures: 

 choroid, the ciliary body and the iris.

5

Delivery of metabolic substrates and oxygen to the retina is accomplished by  (2) 

 the inner retinal and choroidal. 

6

what is the posteriro chamber

Region between the vitreous and the lens.

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7

what produces aqueous humor?

the vascular component of the ciliary body.

8

where is the vitreous humor 

 the space between the back of the lens and the surface of the retina.

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9

what pigment does the macula contain?

 a yellowish pigment (xantophyl). Supports high acuity.

10

The ocular vessels are derived from the

all from the ophthalmic artery (OA),

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11

what are the two distinct vasciualr systems that supply the eye 

 a) the anterior segment (iris and ciliary body)

b) the retinal systems.

12

 Focusing Power of a lens = 

Curvature of surface + differences in Refractive Indexes

13

focal length - how strongly a lens ___

converges light.

14

Greater lens curvature = Greater converging power = __ focal length

Shorter

15

diopters - measure of 

optical power.

16

dipopeter = 

1/focal length

17

emmetropic eye - is

elaxed, unaccommodated, focused on object at “infinity”

18

what is responsible for most of the refraction in the eye

Cornea - 80%

lens does 20%

19

Refractive index of cornea = 

1.37

20

accommodation - the___ to focus on near objects

 curvature of the lens increases

21

what muscles contract to increase the curvature of the lens? which relax?

ciliary muscles contract, zonule fibers relax

22

when the curvature of the lens increases the focal length

decreases

23

Accommodative triad/near reflex:

eye accomm. + pupil constriction + eye convergence

24

eye accomm. + pupil constriction  is mediated by the 

parasymp. nerves from Edwin Westphal nucleus of pretectum

25

The ___ lens is transparent, has crystallins, with high refractive index of 1.42,

crystalline

26

• cataract - disorder of___ that destroys lens transparency,

 lens cell fibers or aggregation of crystallin

27

___ is the leading cause of blindness worldwide.

cataracts

28

risk factors for cataracts 

 aging, diabetes, sunlight, smoking

29

sx of cataracts 

hazy vision, poor night vision, glare, faded colors

30

tx of cataracts includes 

surgical replacement with an artificial lens

31

presbyopia - inability to focus on _____ objects

near

32

Refractive errors prevent light from 

focusing on the retina

33

myopia / nearsightedness is caused by the  

cornea too curved or eyeball too long

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34

with myopia the light is focused ___

in front of the retina 

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35

nearsightedness is called

myopia

36

with -hyperopia / farsightedness the cause is the 

 cornea not curved enough or eye too short

37

with hypoerpopnia the light is focused 

behind the retina

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38

you correct hyperopia with 

(+)/convex lens

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39

you fix myopia with a 

concave lens

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40

Aqueous humor nourishes the__ and ___

 cornea and lens

41

aqueous fumor is secreted by the

epihtelium

42

Aqueous humor

 flows from anterior chamber angle of eye
to...


Leaves the eye by passive flow at the anterior chamber angle

43

 Flow of aqueous humor against resistance generates ___.

intraocular pressure (IOP) of ~15 mmHg

44

Glaucomas = damage to the ___ that can result in vision loss and blindness

optic nerve

45

risk factors for glycoma

high IOP, thin cornea, abnormal optic nerve, HTN, cardiovascular disease, diabetes 

46

glaucoma causes loss of ___ fields 

peripheral 

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47

tx of gluacoma?

treat with

1. eyedrops to decrease aqueous production or increase drainage

or

2. surgery

48

where are photoreceptor cell bodies found?

outer nuclear layer

49

order light passes through to get to the photoreceptor

1. ganglion cell layer

2. inner plexiform laer

3. inner nuclear layer

4. outer plexiform layer

5. out nuclear layer

50

cells in inner plexiform layer 

bipolar / amacrine / ganglion cells synapse

51

cells in inner nuclear layer

bipolar / amacrine / horizontal cell bodies

52

cells in outer plexiform layer

photoreceptor / bipolar / horizontal cells

53

function of pigment epithelium?

 backstop for light, regenerate pigment, nourish and regenerate photoreceptors

54

pigment epithelium in the back of the eye contains ___ pgiment

melanin

55

a lens with a short focal length has ___ focal power

greater

56

Focal distance is ___ proportional to the curvature of the lens.

inversely

57

loss of ___ with cage causes presbyopia

lens elasticity

58

 A diopter of accommodation is defined as 

1/distance to the object

59

. A near object at 1 m requires accommodation of ___

1 D 

1/ ( distance to object)

60

___ requires a positive lense

hypermetropia (positive is a convex lens)

61

Myopic correction using the excimer laser is based on a graded removal of____ tissue to decrease the central anterior corneal curvature.

 central anterior corneal

62

___ correction is based on a graded removal of a peripheral and paracentral anterior corneal curvature.

Hyperopic

63

glaucoma

Open angle: Slow development of pathology caused by obstruction of the___

 drainage canals 

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64

glaucoma

Close angle: Sudden increase in intraocular pressure. Closed or___

 narrow angle between the iris and cornea.

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65

where does phototransduction occur 

in the outer photoreceptor segments

66

 photic input is transmitted to the brain by the spiking discharge pattern of the____ via the optic nerve.

 ganglion cells

67

Retinal glia cells include

astrocytes

microglioa

mueller cells 

68

Vertical information flow:

photoreceptorsbipolar cellsganglion cells

69

Lateral information flow:
Is mediated by 

horizontal cells and amacrine cells

70

Cells along the vertical path (photoreceptors, bipolar and ganglion cells) release ___

glutamate

71

Cells mediating lateral information transmission (horizontal and amacrine cells) release mostly 

 GABA or glycineric 

72

rods and cones are ___

photoreceptors 

73

rods and cones use what NT

glutamate 

74

Photoreceptors in the ___ have a standing/circulating current

Dark

75

Dark

__ and ___ influx at outer segment: depolarization

Ca and Na

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76

Dark

___ at inner segment: hyperpolarization

K efflux

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77

in the dark, the photoreceptor is constantly

staying depoalrized and -40 and releasing glutamate

78

Photoreceptors respond to Light by suppressing the ___

inward, cationic current

79

rhodopsin = pigment in ___

rods

80

cone opsin = pigment in ___

cones

81

Photon absorption makes 11-cis retinal to 

all-trans

82

11-cis retinal to all-trans, activates -->

rhodopsin (rods) or opsin (cones) 

83

Rhodopsin* initiates signal cascade (via transducin and PDE) that___

 decreases cGMP

84

1 Rhodopsin ___ lots of cGMP --> closes 200+ cGMP channels

hydrolyzes

85

↓ cGMP in outer segment -->

 Na and Ca gates close 

86

how does light cuase less Glu release? 

Rhodopsin dec cGMP > Na and Ca gates close -

-> ↓ Na and Ca influx (but K efflux continues) --> h

yperpolarization --> ↓ Glu release & ↓ intracellular Ca

87

____ is the ability of photoreceptors to adjust to the ambient level of light

Light Adaptation

88

light adaption occurs in Occurs in __ and ___

photoreceptors & in postsynaptic retinal cells

89

what happens at saturation? 

 all cGMP-gated channels are closed, photoreceptors cannot respond to further light 

90

rods are cones are very senstiive to light

rods

91

mutation in rod proteins causes ___

retinitis pgimentosa 

92

night blindess, tunnel vision, often legally blind by 40 are sx of 

retinitis pgimentosa

93

1 cone to __ bipolar cell

1

 

rods have a much higher convergence

94

rods or cones mediate high acuity vision?

cones

95

wet
  blood vessels behind retina grow and leak
dry
  degeernation of epithelium and photorceptors, causing dursen build 

age related macular degeration

96

 lose: central vision and acuity

age related macular degeration

97

LGN enters V1 and terminates in___

 layer 4

98

Ouputs to higher areas of v1 is by ___

pyramidal cells

99